The application deals with three separate, but related, projects on the control of cell growth and development. (1) We will investigate the early events associated with the mitogenic response in cells following addition of polypeptide growth factors. The application will focus on the events related to ion transport and changes in intracellular pH measured by novel fluorometric methods devised in this laboratory. (2) We will examine the control of the expression of differentiated cell functions in a muscle cell line associated with cell contact (an inducing signal) and polypeptide factors present in serum (repressive signal). Particular emphasis will be placed on a new post-transcriptional regulation recently identified in this laboratory. Parameters relevant to translational control will also be studied. Creatine phosphokinase and the acetyl choline receptor will be used as the two markers of differentiated cell function. (3) Retinal cell differentiation will be probed by the use of monoclonal antibodies. Cell types of specific monoclonal antibodies will be generated against cells in the chick neural retina at early stages of differentiation by the use of a fluorescent cell sorter technique specifically designed to identify cell specific cell surface antigens. These monoclonal antibodies will be used to probe cell differentiation as well as for separation of different cell types in the neural retina. The differentiation of isolated cell populations will be examined.